Paging universal remote control encoder

ABSTRACT

A paging station remote control system encoder is described. The paging system encoder generates signals in accordance with a predetermined signalling scheme comprising a series of tones and timed pauses and generated in response to control signals supplied either manually or by a paging terminal. The paging system encoder provides control signals which instruct a paging transmitter station to key in the analog or binary modulation mode or to switch from one mode to another without first dekeying the paging transmitter.

This is a continuation of application Ser. No. 487,490 filed Apr. 22,1983, abandoned.

BACKGROUND OF THE INVENTION

This invention relates to the field of the paging base station andterminal communications using both binary signalling and analogsignalling, and more particularly to the signalling scheme and apparatusfor implementing a base station and terminal communications link forinteractively transmitting both binary and analog signals.

In the past a paging base station was required to dekey its transmitterwhen changing from transmission of an analog signal to transmission of abinary signal or vice versa. To initiate an analog page, conventionalpaging systems utilize a sequence of a high level guard tone signal, afunction tone signal and a tone or voice signal accompanied by a lowlevel guard tone signal. To enter a binary paging mode, a prior artremote control paging encoder removes all activity from the remotecontrol link for at least 300 ms causing the transmitter to dekey. Thetransmitter then rekeys in the binary mode after the remote sitereceived a burst of FSK paging signals from the paging system encoder,equivalent to a binary comma for 100 ms.

A prior art paging system of this type is described in Motorola documentnumber 68P06905B33 (1980) entitled "MICOR Tone and Binary PagingTransmitter Station." This instruction manual is available from theService Publication Department of Motorola, Inc., 1301 East AlgonquinRd., Schaumburg, Ill., or from Motorola C & E Parts, 1313 East AlgonquinRd., Schaumburg, Ill.

This is disadvantageous in certain respects. By requiring dekeying ofthe transmitter, a signal such as a binary page followed by a voicemessage must be dekeyed after the binary signal and then rekeyed for theanalog voice portion of the transmission and then dekeyed again andrekeyed for a binary end of transmission message. The result of this wasa noise burst at the end of the voice message and prior to the binaryturn-off code for the pager. The noise burst resulted from the loss ofcarrier from dekeying the transmitter.

It is well known that different modulation techniques are necessary forthe appropriate transmission of binary and analog signals. Therefore, itis desirable to have a technique whereby both analog and binary signalscan be sent to a pager by way of different modulation schemes withoutfirst dekeying the paging base station. Moreover binary pagers withvoice messages require the base station to quickly transfer from ananalog modulation mode to a binary modulation mode, and vice versa.Therefore, it is important to provide a signalling scheme whereby thebase station can perform such a transition with a minimum of effort andwithout introducing extraneous signals that might be picked up by thebinary pager. Also, dekey/rekey reduces system thru-put which isundesirable on heavily loaded channels.

SUMMARY OF THE INVENTION

Briefly described, the present invention contemplates a paging systemremote control encoder which generates and transmits a signalling schemecomprising a series of tones and timed pauses. The paging system encodertransmits a first and second control tone for a predetermined period oftime. If an analog modulation mode is desired, the paging encoderimmediately transmits an analog information signal. If a binarymodulation mode is desired the paging encoder generates a pause and thenin response to a binary input, transmits a binary information signal.

To initiate a binary modulation mode, the paging encoder generates apause immediately following the second control tone, and in response toa binary signal transmits a binary information signal.

It therefore is an object of this invention to provide an improvedpaging system encoder which rapidly instructs a paging base station tokey in an analog or binary modulation mode.

It is a further object of this invention to provide an improved pagingsystem encoder.

It is a further object of this invention to provide a paging encoderwhich allows a paging base station to switch from an analog to a binarymodulation mode without first dekeying the transmitter in order for thebase station to make a transition from one transmission state to theother.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a and 1b are block diagrams of two paging systems of the typewhich utilize an encoder according to the present invention.

FIGS. 2a-f show a specifically formatted signalling scheme used in acommunication link between a paging terminal and a paging base stationwhich incorporates an encoder according to the invention.

FIG. 3 is an electrical schematic of an encoder which generates therequired signalling illustrated in FIG. 2 to the paging base station.

FIGS. 4 through 15 are flow diagrams which define the operation of themicrocomputer used in the encoder of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a block diagram of a paging system of the type whichembodies the signalling scheme utilized in the present invention. Theillustrated paging system includes a paging terminal (10) adapted toprovide analog or binary paging signals. The paging terminal interfaceswith a modem 12 and a paging system encoder 14. The modem 12 is aconventional device which converts a binary signal from the pagingterminal 10 to a frequency-shift keying (FSK) signal used by the stationencoder 14. The paging terminal 10 cooperates with the paging systemencoder 14 by providing signals to the encoder 14 which indicate thatthe paging terminal 10 is about to transmit binary or analog signals.The encoder 14 then signals the paging terminal 10 when the encoder isready to receive either type of signalling. An exact description of thepaging terminal and the interface signals required by the paging systemencoder are described in Motorola document 68P81063E15 (1982) entitled"Simulcast System Controller and PURC Station Controller" available fromthe Service Publication Department of Motorola, Inc., 1301 EastAlgonquin Rd., Schaumburg, Ill. or from Motrorola C & E Parts, 1313 EastAlgonquin Rd., Schaumburg, Ill.

The encoder 14 then generates a series of tones and timed pauses whichare especially formatted and communicated to a paging base station whichincludes station decoder 16. The paging system decoder is described incopending patent application entitled Paging Universal Remote ControlDecoder by Dunkerton et al., Ser. No. 487,488 filed Apr. 22, 1983 andassigned to the assignee of the present invention. The decoder 16converts the formatted signals from the encoder 14 and selectivelyactivates modem 18 and transmitter 20 in predetermined timed sequencesas determined by the signals from the encoder 14. The paging transmitter20 can then be seletively switched between analog or binarytransmissions in response to the signals received from the encoder 14.

The paging system encoder and decoder can be connected in several ways.FIG. 1a shows an encoder and decoder being connected through aterrestrial wire-line. Referring now to FIG. 1b, the paging systemencoder and decoder can also be connected through a communications linkprovided by a radio link transmitter 22 and a radio link receiver 24. Inaddition, the paging system signalling scheme can be expanded to controlany number of simulcast paging transmitter remote sites 26, as shown inFIG. 1b.

The signalling scheme shown in FIG. 2 has been developed to unify thebase station control functions required in paging systems utilizing bothbinary and analog signalling. Most commonly, the analog signalling is inthe form of sequential tone signalling. For the base station there arethree modes of operation: (1) binary (FSK signalling), (2) audio(sequential tone signalling or tone and voice signalling), and (3)combinations of both binary and audio signalling.

Control of the paging base station is accomplished. from paging terminal10 which operates in conjunction with the paging system encoder 14 andis located either remotely or locally with respect to the pagingtransmitter 20. FIGS. 2A through 2F show that the station controlsequence is preferably initiated by a high level guard tone of 2175Hertz for a period of 120 to 140 milliseconds followed immediately by a40 millisecond tone F1 of 1950 Hertz. These two sequential tones aretransmitted by the encoder 14 and are intended to signal the basestation to turn on its transmitter in preparation for transmitting abinary or analog signal to a pager unit. The paging base station needonly be rekeyed if more than 350 milliseconds have lapsed since the lasttransmission.

A combination of binary data and analog data transmission is requiredfor paging systems with mixed binary and tone signalling or tone andvoice pagers which use binary signalling. The timing scheme in FIG. 2Athrough 2F allows interactive analog and digital paging without dekeyingthe transmitter. FIGS. 2A through 2F show the time spacing of analog andbinary signals that are preferred for the paging base station to respondappropriately. In FIGS. 2A, 2B, 2D and 2E it can be seen that fortransmission of a binary signal after a high level guard tone-functiontone is sent, a pause of 130 to 150 milliseconds is preferably insertedinto the transmission before sending the binary data. The pause of a 130to 150 milliseconds tells the decoder at the paging base station thatthere is no analog data and it allows transfer to a binary modulationmode upon receipt of binary data.

If analog data is to be sent immediately following a binary datatransmission, a pause of 50 milliseconds is inserted between the end ofthe binary data and the beginning of the high level guard tone signal(G1). This insures that the paging base station has sufficient time toreturn to a condition in which it can sense a high level guard tone.Note in FIG. 2A that after the binary data has been received andtransmitted by the paging base station and a pause of approximately 50milliseconds has elapsed, only the high level guard tone need betransmitted to the paging base station to enable the paging base stationin a analog modulation mode. The function tone is no longer necessarysince the paging base station has been keyed previously and insufficienttime has elapsed between pages to cause the base station to dekey.

Referring to FIG. 2A, a remote or local terminal transmits to a pagingbase station a guard tone function tone sequence G1, F1 to instruct thebase station transmitter to key. After the guard tone-function tonesequence has been transmitted to the paging base station and has beenreceived by it, the paging base station is immediately in a modulationmode that is appropriate for analog data. FIG. 2C illustrates thiscondition. Binary data is sent only after a 130 to 150 millisecond pauseafter the guard tone-function tone sequence. The binary data is sent tothe base station via a modem 202 format (1200/2200 Hertz signalling)which is well known. Audio data may be sent immediately after the guardtone-function tone sequence along with a low level guard tone.

To initiate an analog modulation mode, a pause of approximately 50 ms,for example, follows the termination of the binary data transmissionbefore the high level guard tone is again transmitted. Immediatelyfollowing the second high level guard tone, the analog data (in thiscase a voice) is sent to the base station along with low level guardtone (not shown). A binary turn-off code ends the transmission to thebinary pager and follows the voice message after a 130 to 150millisecond pause in order for the paging base station to know that itmay transfer to a binary modulation mode for the turn off code.

FIG. 2B shows the transmission of a binary only page. The base stationis again keyed by a high level guard tone-function tone sequence. Theappropriate 130 to 150 millisecond pause then follows the function tone.The pause tells the paging base station that there is no analog data andit may transfer to a binary modulation mode in anticipation of thebinary data. The paging base station then receives the binary data afterit has transferred to its binary modulation mode.

FIG. 2C shows the timing scheme for a sequential tone page. The highlevel guard tone-function tone sequence again keys the base station.This time the analog data is immediately transmitted after the functiontone since the paging base station is in a analog modulation modeimmediately following the function tone. Once analog information isreceived in the time period immediately following the function tone, thepaging base station will stay in an analog modulation mode until itreceives a 130 to 150 millisecond pause.

FIG. 2D shows a binary page followed by a sequential tone page. Thefirst portion of the signal stream is the same as shown in FIG. 2B.After the binary data has been sent and received by the paging basestation, a pause of about 50 milliseconds is inserted into thetransmission stream to enable the paging base station to conditionitself to receive a high level guard tone. The high level guard tone istransmitted from the paging system encoder and received by the pagingbase station. The paging base station immediately goes to a analogmodulation mode and modulates the analog data which is immediatelyreceived after the high level guard tone.

FIG. 2E shows the signalling for multiple binary pages sent withoutpause. The timing scheme for multiple binary pages is essentially thesame for a single binary page as shown in FIG. 2B. Binary data is simplysent one after the other without pause after the initial 130 to 150millisecond pause.

FIG. 2F shows a sequential tone followed by a binary page. Again thehigh level guard tone-function tone sequence keys the paging basestation transmitter and also causes the paging base station to enter ananalog modulation mode. The analog data is transmitted from the pagingterminal immediately following the function tone and thus the analogdata is appropriately modulated. The binary data is sent only after thecompletion of the analog data and a 130 to 150 millisecond pause.

In the preferred embodiment, the analog signal from the paging terminalis summed with a control tone that is preferrably the same as the highlevel guard tone, only at a reduced amplitude.

In summary, to enable the binary mode after the high level guardtone-function tone sequence has been transmitted, a pause of 130/150millisecond duration is inserted before sending the binary signal. Ifmultiple binary pages are to be transmitted, the binary data identifyingeach pager should be sent in sequence without pause. Upon completion ofthe transmission of the binary information, approximately 50 millisecondpause must be sent before enabling the audio control in the paging basestation. After the 50 millisecond pause a high level guard tone is sentto the paging base station to enable the analog-audio mode. (Note: Nofunction tone is needed after the initial station control set-up). Ifthe paging base station does not receive a signal for a period of 350milliseconds, the base station will automatically dekey.

If a binary signal is to be transmitted following an analog/audiosignal, the sequence described above must be repeated. That is to say,130 to 150 millisecond pause must follow the guard tone before thebinary data is delivered to the pager base station.

FIG. 3 is an electrical schematic of an encoder which can generate therequired signalling scheme of the present invention. A more detailedelectrical schematic of the encoder circuit of the present invention isillustrated in Motorola document 68P81063E15 entitled "Simulcast SystemController and PURC Station Controller," available from the ServicePublication Department of Motorola, Inc., 1301 East Algonquin Rd.,Schaumburg, Ill., or from Motorola C & E Parts, 1313 East Algonquin Rd.,Schaumburg, Ill. In accordance with the present invention the variousoutputs of a paging terminal are provided to the respective binary,audio and voice inputs of the paging system encoder. The signals areinterfaced through transformers 102, 104 and 106 respectively, whichprovide impedance matching and isolation between the paging terminal andthe paging system encoder. The transformers 102, 104 and 106 are thenconnected to buffer amplifiers 108, 110 and 112 which compensate forgain losses in the binary modem tones, paging tone and voice audiosignals. The amplifers 108 and 110 are connected to variable resistors114 and 116 which provide further compensation between the variouspaging signals. It is desirable to adjust the binary modem tone, audiopaging tones and voice audio tones so they are substantially equal inamplitude when they are connected to summing amplifier 126. Theamplifier 112 is connected to a preemphasis network 122 which conditionsthe voice audio signal and provides a standard frequency shaping used totransmit paging voice audio to remote paging transmitters. Thepreemphasis network is then coupled to an amplifier 128 and a variableresistor 130 to compensate for gain variations in this signal path.Amplifier 128 also includes a match filter to remove the guard tonefrequency. The variable resistors 114, 116 and 130 are then coupled toelectronic mute switches 118, 120 and 124. Mute switches 118, 120 and124 can be any type electronic switch adapted to pass an electricalsignal in response to an electrical control signal. The mute switches118, 120 and 124 are coupled to and controlled by a peripheral interfaceadaptor circuit (PIA) 132.

The outputs of mute switches 118, 120 and 124 are coupled to a summingamplifier 126 which combines the various signals in equal proportions.The summing amplifier is then coupled to an output amplifier 134 whichis coupled to a transformer 136. The amplifier 134 and transformer 136convert the output signal of summing amplifier 126 to a signal ofamplitude and impedance required by the wire-line hookup or transmitterlink used to couple the paging system encoder 14 to the paging systemdecoder 16.

The summing amplifier 126 also receives an input through mute switch 125from the variable resistor 138 which is coupled to a programmableattenuater 140. The programmable attenuator 140 is coupled to twocontrol signals from the peripheral interface adaptor 132 and a toneinput from the low pass filter 142. The low pass filter 142 is coupledto a microcomputer 144. The microcomputer 144 generates the variouscontrol tone sequences of the paging system encoder and provides signalsto the programmable attenuator 140 through PIA 132 to control theamplitude of the control tones coupled to the summing amplifier 126. Themicrocomputer 144 and the PIA 132 also control the operation of the muteswitches in response to several input signals in accordance with thesignalling scheme of the present invention. The present inventionutilizes a widely used microcomputer integrated circuit designatedMC6803 and available from Motorola, Inc. The companion peripheralinterface adapter integrated circuit is designated MC6821 and is alsoavailable from Motorola, Inc.

The paging system encoder 14 is configured to provide direct usercontrol via several switches, 146 through 162, which are disposed on apanel which is accessable to the user of the encoder. The switches 146,148, 150, and 152 are connected to input ports of the PIA 132. Switch146 when closed will cause the paging system encoder to enable the tone,modem and voice paths to be enabled simultaneously to the outputterminal transformer for audio level set. Likewise switch 148 whenclosed will cause a series of audio test tones, generated bymicrocomputer 144 to be placed at the output terminals of the encoder.Switches 152 and 150 are included with the paging encoder circuit toallow the paging system to accommodate additional RF link transmittersto be used in a simulcast system. For example, if a paging transmittersite is located a large distance from the paging terminal site, arepeater site will be included in the system. Each repeater site willrequire a certain amount of time to allow the repeater transmitter tokey and therefore the high level guard tone must appear for an extendedtime to allow retransmission to the paging transmitter site. Each linksite requires approximately 250 ms to retransmit the high level guardtone. Switches 150, 152 are configured to provide a binary encoded inputto the encoder circuit which activates an additional guard tone periodto be generated by the paging encoder. The high level guard tone signalcan be increased in 300 ms increments, and a maximum of 1200 ms can beeffected by switches 150, 152. If both switches 150 and 152 are open, nohigh level guard tone will be added to the normal tone sequence. Ifswitch 150 is open and switch 152 is closed, 300 ms of high level guardtone will be added to the initial tone sequence. Likewise, increments of300 ms can be added to the high level guard tone sequences by providingthe various combinations of switches 150 and 152.

The paging system encoder circuit cooperates with the paging terminal 10of FIG. 1, through the clear to page voice terminal 162, the clear topage binary terminal 160, the key analog terminal 156 and the key binaryterminal 158. In operation, a paging subscriber will activate the pagingterminal 10 of FIG. 1, through a telephone link by signalling thetelephone number assigned to the unique pager address. The pagingterminal 10 will then convert the telephone number to a signalcomprising the exact pager address. The paging terminal 10 then signalsthe paging system encoder that a paging signal is imminent by activatingeither the key analog terminal 156 or the key binary terminal 158depending on the type of pager being signalled. If the key binaryterminal is activated, the paging system encoder will generate theseries of timed tones and pauses which place the paging remotetransmitter in the binary transmission mode. When the transmitter hasbeen properly set up and keyed, the paging system encoder will activatethe clear to page binary terminal, and activate the binary modem tonemute switch 118 to pass modem tones to summing amplifier 126 and outputtransformer 136. Similarly, if the system is to be placed in the analogaudio transmission mode, the paging terminal will activate the keyanalog terminal 156 and the paging system encoder will generate theseries of timed tones and pauses which place the paging remotetransmitter in the analog transmission mode.

FIGS. 4 through 16 are flow diagrams which define the operation of themicrocomputer 144 used in the encoder of FIG. 3. FIG. 4 details theoperation of the initial program sequence when power is first applied tothe paging encoder. Since it is not possible to predict a specific logiccondition which will be present at any particular input or outputterminal of the microprocessor or PIA, the power-up sequence of FIG. 4establishes known conditions on all critical input and output terminals.

When power is first applied to the paging encoder 14, the programcontrol of the microcomputer is configured to execute an initializationprogram 200. The program control then proceeds to item 202 andimmediately sets the microcomputer interrupt mask which insures theprogram will not be interrupted during the power-up sequence. Theprogram then initializes all random access memory variables.

The microcomputer 144 ports can be configured to function as eitherinputs or outputs to the microcomputer and must be configured accordingto program control. As noted in FIG. 3, the microcomputer 144 acts asthe tone sequence generator for the paging system encoder. Any toneswhich may be present at port P2 of FIG. 3 are shut off during thepower-up sequence 200 by designating port P2 as an input. This stepinsures no tones are placed on the output of the encoder circuit untilnecessary.

The microcomputer 144 provides an internal tone generator which iscontrolled according to the state of an internal register. By entering anumerical value in the ENCINC register, a corresponding tone period willbe generated by the tone circuit. According to the next item 206, thetimer control and status register are initialized and subsequently, annumber is loaded into the TCS register, so that the tone output isinitialized. The power-up sequence next designates the PIA ports asinput or outputs.

Referring now to FIG. 3, signals KA, KB, HO1, HO2, TT and OA are coupledto PIA port A. Likewise, signals CTPA, CTPB, M0, M1, M2, M3, AT1, AT2are coupled to PIA port B. In accordance with the present invention,FIG. 4 shows the PIA port configuration. Consequently item 210configures PIA port A as an input and PIA port B configures as anoutput. The power-up sequence next initializes the values associatedwith PIA port B by placing the code on the PIA port B 218 whichcorresponds to opening or inhibiting all mute switches 118, 120, 124,125 of FIG. 3, inhibiting the clear to page signals 160, 162 of FIG. 3and by adjusting the programmable attenuator 140 of FIG. 3 for maximumattenuation.

The paging system encoder makes decisions as to what subsequent actionsto effect based on two integral system status Bytes which are anindication of the system's past and present activity. The system statusbytes are designated New Status (NSTAT) and Old Status (OSTAT). Sincethe system operation will be affected by the old system status, forinstance an analog to binary transition, this byte must be initializedduring the power-up sequence. Item 220 sets the system status byte OSTATto a code comprising all binary ones, which indicate that the system iscurrently dekeyed.

The paging system encoder is now configured with initial conditions incritical areas which will ensure correct system operation. Subsequently,the interrupt mask is cleared 222, thus allowing the microprocessor toexecute interrupt commands. Timeout period 224 is provided to allow allinitial conditions on the system to stabilize. The paging encoder nowenters the SCAN mode 300.

Referring now to FIG. 5, there is illustrated a flow chart embodying thescan method of the present invention. The flowchart in FIG. 5 provides adetailed description for the process steps necessary for implementingthe scan method of the present invention in the paging system encoder 14in FIG. 3. The scan routine forms the basic background operating schemeof the present invention. The primary task for the scan routineinterprets key input commands from either hardware front panel switchesor from the paging terminal and exits to one of five tasks depending onthe condition of the key switches.

When the scan routine is activated, item 302 retrieves the system statusbits D6 from the systeem status bytes NSTAT and OSTAT.

Referring now to decision 306, if both system status bytes NSTAT andOSTAT show a binary 1 in D6, which is an indication of the hardwarepanel key switch, then the system is dekeyed, and program will enteritem 304. If either data bit D6 from NSTAT or OSTAT is a binary zero,the hardware panel key switch has been changed and the program willenter the panel key handler (PKHNDL) routine 308. Item 304 retrieves thesystem status bits D1 and D.0. from the system status bytes NSTAT andOSTAT. Status bits D.0. and D1 of NSTAT indicate whether the pagingsystem encoder is being signalled, that is either an analog or binarypaging signal is imminent from the paging terminal 10 or modem 12 ofFIG. 1. Decision 310 then compares system status bits D1 and D.0. whichindicate if a key command has been received from the paging terminal. IfNSTAT has not changed from the previous period OSTAT, the programreturns to the initial item of the scan routine and continues searchingfor a change.

If NSTAT has changed the system will enter item 316, which provides a 5ms time delay. This time delay provides enough time to detect a keybounce or an erroneous input. Decision 318 compares the key bit D.0. orD1 with the state of the key bit D.0. or D1 5 ms earlier. If a keybounce is detected, decision 318 returns program control to the firststep of the scan routine.

If a key bounce was not detected, the program proceeds to decision 320which examines the D.0. and D1 status bits in the OSTAT status byte. Ifthe D.0. and D1 status bits show 00 which is an impossible condition atthis point in the program, the program control will exit decision 320and proceed to error routine 334. If an error is not detected theprogram proceeds to decision 322. If the system has been previouslykeyed in either the analog or binary mode, the program will proceed todecision 326. If the system was not previously keyed, the program willexit the scan routine and proceed to the select modulation (SELMOD)routine 370, which will be discussed in more detail later.

As noted previously, if the paging system has been previously keyed theprogram will proceed to decision 326. At this point, the paging systemwill either dekey or change transmission modes.

If the system status bits D1D0 of NSTAT and OSTAT indicate the sytem waspreviously keyed and is now required to dekey, the program will proceedto the dekey routine 330. Alternatively, if the system status bits D1D0of NSTAT and OSTAT indicate the system should remain keyed, but inanother mode, the system will enter the modulation change routine 328.

The modulation change routine 328 occurs in mixed paging systems whenbinary pages are sent immediately after a tone-signalled page or visaversa. As previously discussed, mode information is carried on thesystem status bits D1D0. Item 350 retrieves the NSTAT status bits D1D0.Item 352 compares the NSTAT status bits with the OSTAT status bits. Ifthe NSTAT status bits D1D0 are both equal to binary zeros, a racecondition or overlapped key request is indicated. Decision 354 will thenpass program control to item 356 which will then update the NSTAT statusbyte to the current valve of OSTAT and subsequently select the statusupdate routine (REPOLL) 346.

If either NSTAT or OSTAT contains a binary one in D1DO, the program willproceed to decision 360. If the OSTAT status bits D1D0 show 10 and theNSTAT status bits show 01, an analog to binary transition is indicated,and decision 360 will select the AUDBIN routine 362, which will bediscussed in more detail later. If AUDBIN is not selected, the Programwill proceed to decision 364. If the OSTAT status bits D1D0 show 01 andthe NSTAT status bits show 10, decision 364 will select the binary toanalog transition routine (BINAUD) 368. If BINAUD is not selected, anerror has occurred and decision 364 will select the error routine 334.

If the error routine 334 is selected, Item 332 will reset the NSTATstatus byte value to the normal value (D1D0=11) indicating the systemshould be dekeyed. The Item 332 then selects the dekey routine 330.

When invoked, dekey routine 330 will execute the tasks required to dekeyor turn off the paging transmitter stations and reset the paging encoder14 for the next key-up sequence. The dekey routine begins with item 338which designates microcomputer port P2 of FIG. 3 as an input, thusturning off any tone appearing on the port. The program proceeds toitems 340 and 342 which updates the PIA port B bit status instruction sothat the audio mute switches 118, 120, 124 and 125 of FIG. 3 are set tomute the signal paths, and so that the programmable attenuator is setfor maximum attenuation. The program proceeds to item 344 which providesa waiting period required by the paging system to dekey. Item 344 thenproceeds to the REPOLL routine 346. This routine is the end of thebackground loop. It updates the current status of the paging systemencoder. Item 348 replaces the contents of the OSTAT register with theNSTAT status values, and then returns the program to the beginning ofthe SCAN routine 300.

Referring now to decision 322, if the system status bits indicate akey-up condition, the program will proceed to the modulation selectionroutine, SELMOD, routine 370. FIG. 5b shows the program sequence forSELMOD. The SELMOD routine 370 selects one of two sequencing tasks to beperformed by the paging system encoder, depending on the system statusbits D1D0 which indicate the key analog and key binary signals of thepaging terminal. Item 374 reads the NSTAT status bit for any keyingactivity. If both status bits D1D0 are binary zeros, a race condition isindicated, and decision 376 will select Item 378 giving binary priorityif both analog and binary key requests are simultaneous. Item 378 willupdate the NSTAT variables D1D0 to a 01 condition and select the key binroutine 386.

If the NSTAT variables D1D0 show a non-zero condition, a decision 376will select decision 380. If the system status bits D1D0 indicate ananalog page, decision 380 will select the KEYAUD routine 382. If KEYAUDis not selected, the program will select decision 384. If the systemstatus bits indicate a binary page, decision 384 will select the KEYBINroutine 386. If KEYBIN is not selected, decision 384 will select errorroutine 334.

Referring now to FIG. 6, there is illustrated a flowchart embodying thepanel key handler routine (PKHNDL) of the present invention. The PKHNDLroutine 308 is used anytime the hardware panel key switch is activated.PKHNDL 308 begins with decision 402 which examines the NSTAT and OSTATD6 status bits for any change. If no change is detected, decision 402selects the Repoll routine 346. If a change is indicated, decision 402will select item 406 which generates a 5 ms time pause in the program.Decision 410 examines the D6 data bit for a key bounce. If a key bounceis detected, program control will be returned to the SCAN routine 300.If a key bounce is not detected, the program proceeds to decision 412which selects item 416, if a dekey command has been detected. Item 416then clears the clear-to-page inhibit flag, and the program proceeds tothe ERROR routine. No real error has occurred here, but the ERRORroutine provides a proper status reset for a panel key operation.

If a dekey command is not detected, decision 412 will select item 414,sets the clear-to-page inhibit flag and sets the test tone sequence tostep 0. Item 418 then sets the programmable attenuator 140 and audioswitches 118, 120, 124 and 125 to the mute condition. Item 422 thenprovides a 500 millisecond time delay before selecting the KEYAUDroutine 382, since a hardware panel key can only activate the analogmode.

FIG. 7 shows a flowchart embodying the analog key-up routine (KEYAUD)382 of the present invention. KEYAUD 382 is selected when the pagingsystem encoder is to key up in the analog mode. KEYAUD sequences thetone attenuator, calls the tone sequencer and enables the tone and audiosignal paths. It then signals the paging terminal when the paging systemis clear to page.

When selected, KEYAUD proceeds to item 450 which selects the high levelguard tone subroutine (HLGT) 450. HLGT causes the high-level guard tonesequence to be placed at the output of the paging encoder. This will bediscussed in more detail later. When completed, HLGT returns programcontrol to item 452 which adjusts the programmable attenuator 140 ofFIG. 3 for mid-level attenuation. Item 454 then sets the ENCINC or tonegenerator register to produce the function tone frequency. Item 456 anddecision 458 cause the function tone to be produced by themicroprocessor for 40 ms. When the function tone period has elapsed, theprogram will proceed to item 460 to generate a guard tone signal theprogram will proceed to item 462 which adjusts the programmableattenuator 140 of FIG. 3 to a low level corresponding to the levelrequired by the low level guard tone. Subsequently, item 464 opens muteswitch 124 and item 466 opens the mute switches 120, 125. Decision 468examines the clear to page inhibit flag. If the clear to page inhibitflag is set, because of a hardware panel key, the decision 468 willselect the REPOLL routine 344. If the clear to page inhibit flag is notset, decision 468 will select item 470 which enables the clear to pageanalog line and inhibits the clear to page binary line.

Referring now to FIG. 8, there is illustrated a flowchart embodying thebinary key routine (KEYBIN) of the present invention. When activated,KEYBIN proceeds to item 500 which calls the HLGT routine 450. Whenexecuted, HLGT will return program control to item 502 which adjusts theprogrammable attenuator 140 of FIG. 3 for mid-level attenuation. Theprogram then proceeds to item 504 which adjusts the ENCINC register toproduce the function tone frequency. Decision 508 causes this tone to beplaced at the output of the paging encoder for 40 ms. The program thenexecutes item 510 which sets the programmable attenuator 140 of FIG. 3and mutes attenuator mute switch 125.

Item, 520 then designates microcomputer port P2 as an input, thusinhibiting any tone output from the microprocessor. Item 522 anddecision 524 then cause the microprocessor to pause for a time period sothat a 150 ms. pause will appear at the output of the paging encoder.When 150 ms. has elapsed, item 526 sets the "comma" counter for thedesired number of comma cycles, and Item 528 calls the comma routine528. This will be discussed in more detail later. The program thenproceeds to Item 530 which enables the clear to page binary line,inhibits the clear to page analog line and opens the binary modem tonesignal path. The program then selects the REPOLL routine 344.

Referring now to FIG. 9, there is illustrated a flowchart embodying theHigh-level guard tone (HLGT) routine of the present invention. TheHigh-level guard tone signal signals a paging transmitter site that apaging signal is imminent and the transmitter should turn on. In asystem which uses link stations to connect the remote stations,additional periods of High-level guard tone are required to allow eachstation along the link to receive the High-level guard tone frequency.

The HLGT routine begins with item 550, which reads the NSTAT Hop selectdata bits D2D3 which reflect the user selectable internal hardwarecondition of switches which provide information as to how many linktransmitters are in use and subsequently, what time period of High-levelguard tone is required. The program then proceeds to item 552 whichadjusts the ENCINC register to generate a guard tone frequency. Item 554then adjusts the programmable attenuator 140 of FIG. 3 for high level orminimum attenuation and then opens the microcomputer tone mute switch125. Item 556 then designates microprocessor port p21 of FIG. 3 as anoutput, thus enabling the tone output of the microprocessor. The programthen proceeds to decisions 558, 560, 562 which examine the NSTAT statusbits D2D3 to determine the number of HLGT periods required. If noadditional guard tone is required, decision 558 will select item 570which will cause HLGT to be generated for 120 ms. Similarly, if onetransmitter hop is required, decision 560 will select item 572, whichwill cause HLGT to be generated for 420 ms. If two hop periods arerequired, decision 562 will select item 566 which will cause HLGT to begenerated for 720 ms. Otherwise, item 564 will be selected, and HLGTwill be generated for 1020 ms. Decision 568 examines items 570, 572, 566or 564 and evaluates the elapsed time depending on which item wasselected. When the HLGT sequence has elapsed, decision 568 will returnthe program control to the subroutine which selected the HLGT routine.

FIG. 10 shows a flowchart demonstrating the Binary to Analog (BINAUD)routine of the present invention. BINAUD is involved whenever the pagingsystem is transmitting in a binary mode and shift to the analog pagingmode is required. BINAUD causes the paging system to wait for 50 ms.,then provides high-level guard tone, then low-level guard tone to thepaging transmitters. The tone and voice signal paths are enabled, andthe clear to page analog signal is activated.

BINAUD begins with item 600 which inhibits the clear to page binarysignal and mutes the binary modem tone signal path, thus terminating thebinary signal transmission. Item 602, then activates the timer routinesand decision 604 causes the paging encoder to generate a 50 ms pause.When 50 ms has elapsed, item 606 stores the NSTAT status byte in atemporary location. Item 608 then loads a new value into the NSTATstatus byte which indicates that zero transmitter hops are required. Asnoted previously, the system status bits D2D3 indicate a number of linktransmitters in a system which would require an additional High-levelguard tone signal. However, since the paging system is alreadytransmitting, additional high-level guard tone is not required, and,therefore, item 608, temporarily loads a zero value into the D2D3 systemstatus bits of NSTAT. The program then proceeds to item 610 which callsthe HLGT routine which generates the high-Level guard tone frequency.When HLGT has been executed, the program proceeds to item 612 whichrestored the NSTAT byte with the value previously set aside in thetemporary NSTAT location. Item 614 then sets the programmable attenuator140 of FIG. 3 for high attenuation so that the microprocessor willcontinue to generate low-level guard tone which is required to keep thepaging transmitters in the analog paging mode. Item 616 then opens thepaging tone and voice signal paths by opening mute switches 120 and 124of FIG. 3. Item 618 then enables the clear to page analog signal, andthe program then selects the REPOLL routine.

Referring now to FIG. 11, there is illustrated a flowchart embodyinganalog to binary transition routine (AUDBIN) 362. The AUDBIN routineprovides the paging system encoder control sequence required for a mixedmode paging transition from analog to binary. The AUDBIN routine causesthe paging system encoder to mute all audio signal paths, waits 150 msand then generates a burst of comma tones which causes the pagingtransmitters to enter the binary transmission mode. The binary modemsignal path is then opened, and the clear to page binary signal isenabled.

The AUDBIN routine 362 begins with item 650 which updates the PIA port Bdesignations. Item 650 disables the clear to page analog signal, mutesall open audio paths and adjusts the programmable tone attenuator formaximum attenuation.

The program then proceeds to item 652 which sets the timer routine togenerate a 150 ms time period. The timer routine will be discussed inmore detail later. Decision 656 then checks for the termination of the150 ms time-out period. Item 658 then adjusts the comma counter togenerate 8 comma sequences, and item 528 then executes comma generator(COMGEN) routine 528 which causes the paging transmitters to enter thebinary transmission mode. Item 662 then opens the binary modem tone muteswitch 118 of FIG. 3. The program then proceeds to item 664 whichenables the clear to page binary signal. The program then selects theREPOLL routine 346.

Referring now to FIG. 12, there is illustrated a flowchart embodying thebinary comma generator routine (COMGEN) of the present invention. COMGENgenerates a burst of (N) mark-space modem tone sequences of standardtone frequencies at 1200 Hz or 2200 Hz for asynchronous modems.

COMGEN begins with item 700 wh1ch disables all clear-to-page signals,opens the modem tone mute switch 128 of FIG. 3 and adjusts theprogrammable attenuator 140 of FIG. 3 for mid-level attenuation. Theprogram then proceeds to item 704 which instructs the microprocessor togenerate a 1200 Hz signal by loading the ENCINC register and designatingmicrocomputer port P2 as an output. Item 706 then generates a timeperiod which causes the 1200 Hz signal to be generated or 1.6667 ms.This signal comprises a FSK binary one. The program then proceeds toitem 708 which instructs the microprocessor to generate a 2200 Hz signalby addressing the ENCINC register item 710 and then causes the 2200 Hzsignal to be generated for 1.818 ms. This signal comprises a FSK binaryzero. When this time has elapsed, item 712 will decrement the commacounter which was initialized by the routine utilizing the COMGENroutine. Decision 714 examines the comma counter register. If the commacounter is currently a non-zero value, decision 714 will return programcontrol to item 704. If the comma counter contains a zero value, theprogram will proceed to item 716 which designates microcomputer port P2as an input, thus inhibiting the microprocessor tone generator. Item 716also closes the attenuator mute switch, disables all clear-to-pagesignals and sets the programmable attenuator or maimum attenuation. Item718 then returns program control to the routine which activated COMGEN.

Referring now to FIG. 13, there is illustrated a group of flowchartsembodying the time delay generator routines of the present invention.These routines are utilized whenever the microprocessor is required togenerate tones or pauses for a specific period of time, as well as anyother task which requires a timekeeping function.

FIG. 13a shows a flowchart illustrating the timer set routine TSET whichis called by background routines anytime an elapsed time timer is to beset up. The microprocessor 144 of FIG. 3 utilizes a 16-bit free-runningcounter register (FRR) to generate time information. In addition, asecond 8-bit register (TIME) is utilized. Whenever the free-runningregister contains all binary one's, an overflow will activate the TOFINinterrupt routine which will increment the value stored in TIME.Therefore, subsequent overflows will be accumulated in TIME via theTOFIN interrupt routine.

The TSET routine 750 begins with item 752 which saves the values storedin FRR and the index register. The program proceeds to item 754, andcaptures the present time as indicated by the value of FRR. Item 756then retrieves the required time delay value and adds this value to thevalue stored in FRR (most significant byte of FRR) and TIME. This targetvalue will be an indication of the value of most significant byte of FRRand TIME when the desired time has elapsed. Item 758 then restores theregisters and stores the computed time in a target register, (TARGET),and program control returns to the routine which activated TSET.

FIG. 13c illustrates a flowchart showing the timer interrupt overflowroutine (TOFIN) of the present invention. This routine is entered everytime the value stored in FRR increments to a value represented by abinary one in every bit of the register.

TOFIN begins with item 770 which clears the timer overflow interruptflag allowing the timer to generate an interrupt during the subsequenttimeout. Item 772 then increments the value stored in TIME. Item 774then services the watchdog timer. The watchdog timer is a hardwaredevice which prevents runaway conditions in the microcomputer 144. Ifthe watchdog timer is not addressed within a predetermined period, thetimer will reset the microprocessor. Item 774 will then return programcontrol to the routine being executed when the interrupt occurs.

FIG. 13b shows the timer compare interrupt handler routine (TONOUT)which generates a square-wave signal, and is used for tone encoding.TONOUT generates a tone frequency based on the value stored in theENCINC register. TONOUT can generate frequencies which range from 300 to3000 Hz.

TONOUT is activated anytime the value of an internal register (TCOMPR),related to the value of ENCINC, is equal to the value of thefree-running register. When the TCOMPR value is equal to the value ofthe free-running register, an interrupt will activate TONOUT 760. Item762 will then toggle the microprocessor port P2. Item 764 then updatesthe TCOMPR register to generate an interrupt a half period later. Item764 subsequently returns the program control to wherever the program waswhen it was interrupted.

Referring now to FIG. 14, there is illustrated a flowchart embodying thetimer check routine TCHK of the present invention. The TCHK routinedecides whether the timer interval, previously established by the TSETroutine, has elapsed. It is called by the background routines whichutilize the target parameter of FIG. 13. TCHK captures the present timefrom TIME and the M.S. byte of FRR in Items 804 and 812. Item 802 savesthe TARGET time value.

Items 816 thru 856 test present time compared to TARGET time. If presenttime equals or exceeds TARGET, TCHK returns control to the callingroutine with Carry Bit Set. Otherwise control is returned with CarryClear.

The mathematics of checking for "greater than" or "less than" iscomplicated by the fact that the incremented TIME value will eventuallyset the most significant bit. Once set, TIME is considered a Negativenumber for math functions and would test as "less than" the TIME valuejust before the MSB was set. Much of the logic discussed below dealswith reconciling this anomaly.

TCHK 800 begins with item 802 which saves the values contained in theindex and target registers and sets the interrupt mask 804. Item 804retrieves the value stored in the TCSR register and also retrieves thevalue of the TIME register and FRR most significant byte. If thesevalues indicate that an interrupt which would activate TOFIN is pending,decision 806 will select item 808 which increments the value stored inTIME and resets the watchdog timer. The program will then proceed toitem 812. If an interrupt is not pending, decision 806 will select item812 directly. Item 812 retrieves the value stored in TIME, and item 814clears the interrupt mask.

Decision 816 compares the values of the previously stored TARGET andTIME registers. If the values stored in TIME have the same sign theprogram will proceed through decision 818. If the target value is alsopositive decision 818 will direct program control to TSAME by selectingitem 836, which calculates the differnce between the TIME and TARGETregisters. If TIME minus TARGET is greater than zero, decision 838 willreturn program control to the subroutine which selected TCHK. If thevalue of TARGET minus TIME is less than zero, the program proceeds tothe NOTYET routine 842 by selecting item 844. Item 844 clears the carrybit. The program then proceeds to item 848 which resets the watchdogtimer and restores the TARGET and index registers and returns programcontrol to the subroutine which selected TARGET.

Referring back to decision 818, if the value stored in time is positive,and the value stored in target is negative, decision 818 selects item822 which calculates a new value for TIME based on an estimate of themaximum amount of time which could have elapsed since the routine wasactivated. This new value is known as the latency period. If the newvalue of TIME is still positive, the routine will select NOTYET 826. Ifthis new value of time is now negative, the program will proceed toCOMMON 828.

Referring now to decision 816, if TIME is negative, the program selectsdecision 830. If the value stored in TARGET is negative, the programproceeds to TSAME 832. If the value stored in TARGET is positive,decision 830 will select item 834, which calculates a latency period ineactly the same manner as item 822. Item 834 then proceeds to decision840 which evaluates the new value of time.

If the new value of TIME shows a negative value, the program willproceed to NOTYET 842. If the new value of TIME is positive, decision840 will select COMMON 828.

COMMON 828 begins with item 850 which calculates a value equivalent toTIME-TARGET. The program then proceeds to decision 852. If the newcalculated value is negative, decision ]52 selects item 856 which setsthe carry bit and then selects the RET routine 846. If the newcalculated value is positive, decision 852 selects the NOTYET routine826.

In summary, a paging system encoder capable of generating a series oftimed tones and pauses in accordance with a predetermined signallingscheme has been described. The paging system encoder provides signalswhich instruct a paging base station encoder to key in an analog orbinary modulation mode or to make a transition from one mode to another.Accordingly, other modifications, uses and embodiments will be apparentto one skilled in the art without departing from the spirit and scope ofthe principles of the present invention.

What is claimed is:
 1. A method of formatting control tones, binaryinformation signals and analog information signals for outputtingthereof to a paging base station, over a single linking channel whichallows the base station to continuously transmit a sequential analog orbinary signal without dekeying the base station transmitter between saidanalog or binary signals, said method including the steps of:(a)sequentially transmitting first and second control tones for apredetermined period of time over said linking channel to activate saidbase station for the transmission of an analog or binary paging signals;(b) in response to an analog key request input immediately outputtingover said linking channel for transmission by said base station, ananalog information signal followed by a pause and then, in response to abinary input, outputting a binary information signal; and (c) in theabsence of said analog key request input, generating a pause for apredetermined period of time following said second control tones, and,in response to a binary key request input, outputting over said linkingchannel for transmission by said base station a binary informationsignal.
 2. A paging transmitter remote control encoder for cooperatingwith a paging terminal and receiving paging signals comprising binarymodem tones, audio paging tones and voices audio from said pagingterminal and combining said paging signals with transmitter controltones, said encoder comprising:(a) means for inputting the pagingsignals; (b) means responsive to paging requests from a paging terminal;(c) means for inputting paging terminal first and second controlsignals, said paging terminal control signals indicating analog orbinary paging information is available for transmission; (d) means foroutputting paging terminal third and fourth control signals indicatingproper time to release said paging information; (e) means coupled tosaid input means for amplifying and equalizing said inputted pagingsignals; (f) means for outputting an encoder output signal, said encoderoutput signal comprising the inputted paging signals; (g) means forselectively coupling said paging signals in a predetermined sequencebetween said amplifying and equalizing means and said output means; (h)means for inputting a local override of paging encoder control signalsfor halting encoder operation in a predetermined state; and (i) meansfor selectively gating said third and fourth paging terminal controlsignals for arbitration if said first and second control signals appearsimultaneously.
 3. The apparatus of claim 2 wherein said first andsecond terminal control signals comprise an analog or binary pagerequest indication.
 4. The apparatus of claim 2 wherein said third orfourth terminal control signals include an analog or binaryclear-to-page indication.
 5. The apparatus of claim 3 wherein said firstor second signals indicate a key request from terminal to encoder. 6.The apparatus of claim 4 wherein said third and fourth signals comprisea clear to page from encoder back to terminal busying the terminal untilpaging information can be accepted by the encoder.
 7. The apparatus ofclaim 4 wherein said third and fourth signals comprise a means ofarbitration between multiple terminal inputs for orderly flow of paginginformation without dekeying base stations.
 8. The apparatus of claim 4wherein said third and fourth signals comprise a means of arbitrationbetween analog and binary sections of a paging terminal allowing orderlyflow of paging information without dekeying base stations.
 9. A methodfor encoding simulcast transmitter remote control signals forcooperating with a paging terminal and receiving paging signalscomprising binary modem tones, audio paging tones and voice audio fromsaid paging terminal and combining said paging signals with transmittercontrol tones, said method comprising the steps of:(a) amplifying andequalizing said inputted paging signals; (b) inputtting first and secondpaging terminal control signals, said paging terminal control signalsindicating analog or binary paging information is available fortransmission; (c) outputting third and fourth paging terminal controlsignals indicating the proper time to release said paging information;(d) selectively gating said third and fourth paging terminal controlsignals for arbitration if said first and second control signals appearsimultaneously; (e) inputting the paging signals; (f) selectivelycoupling said paging signals in a predetermined sequence, and outputtingan encoder output signal; and (g) inputting a local override of pagingencoder control signals for halting paging encoder operation in apredetermined state.